OnApplicationPause problem Time

I have a daily reward. When the game enters OnApplicationPause the time does not continue. unless I use Application.Quit and enter again Please if you know what I should write down at OnApplicationPause

using System; using System.Collections; using System.Collections.Generic; using UnityEngine; using UnityEngine.UI; using Unity.Notifications.Android; using UnityEngine.SceneManagement;

public class DailyReward : MonoBehaviour {

 //UI
 public Text timeLabel; //only use if your timer uses a label
 public Button timerButton; //used to disable button when needed
 public Image _progress;
 //TIME ELEMENTS
 public int hours; //to set the hours
 public int minutes; //to set the minutes
 public int seconds; //to set the seconds
 private bool _timerComplete = false;
 private bool _timerIsReady;
 private TimeSpan _startTime;
 private TimeSpan _endTime;
 private TimeSpan _remainingTime;
 //progress filler
 private float _value = 1f;
 //reward to claim
 public int RewardToEarn;
 public GameObject press;
 [SerializeField]





 //startup
 void Start()
 {
     if (PlayerPrefs.GetString("_timer") == "")
     {
         Debug.Log("==> Enableing button");
         enableButton();
     }
     else
     {
         disableButton();
         StartCoroutine("CheckTime");
     }
 }



 //update the time information with what we got some the internet
 private void updateTime()
 {
     if (PlayerPrefs.GetString("_timer") == "Standby")
     {
         PlayerPrefs.SetString("_timer", TimeManager.sharedInstance.getCurrentTimeNow());
         PlayerPrefs.SetInt("_date", TimeManager.sharedInstance.getCurrentDateNow());

     }
     else if (PlayerPrefs.GetString("_timer") != "" && PlayerPrefs.GetString("_timer") != "Standby")
     {

         int _old = PlayerPrefs.GetInt("_date");
         int _now = TimeManager.sharedInstance.getCurrentDateNow();


         //check if a day as passed
         if (_now > _old)
         {//day as passed
             Debug.Log("Day has passed");
             enableButton();

             return;
         }
         else if (_now == _old)
         {//same day

             Debug.Log("Same Day - configuring now");
             _configTimerSettings();
             return;
         }
         else
         {
             Debug.Log("error with date");
             return;
         }
     }
     Debug.Log("Day had passed - configuring now");
     _configTimerSettings();
 }

 //setting up and configureing the values
 //update the time information with what we got some the internet
 private void _configTimerSettings()
 {
     _startTime = TimeSpan.Parse(PlayerPrefs.GetString("_timer"));
     _endTime = TimeSpan.Parse(hours + ":" + minutes + ":" + seconds);
     TimeSpan temp = TimeSpan.Parse(TimeManager.sharedInstance.getCurrentTimeNow());
     TimeSpan diff = temp.Subtract(_startTime);
     _remainingTime = _endTime.Subtract(diff);
     //start timmer where we left off
     setProgressWhereWeLeftOff();

     if (diff >= _endTime)
     {
         _timerComplete = true;
         enableButton();

     }
     else
     {
         _timerComplete = false;
         disableButton();
         _timerIsReady = true;
     }
 }

 //initializing the value of the timer
 private void setProgressWhereWeLeftOff()
 {
     float ah = 1f / (float)_endTime.TotalSeconds;
     float bh = 1f / (float)_remainingTime.TotalSeconds;
     _value = ah / bh;
     _progress.fillAmount = _value;
 }



 //enable button function
 private void enableButton()
 {
     timerButton.interactable = true;
     press.SetActive(true);
 }



 //disable button function
 private void disableButton()
 {
     timerButton.interactable = false;
     press.SetActive(false);


 }


 //use to check the current time before completely any task. use this to validate
 private IEnumerator CheckTime()
 {
     disableButton();

     Debug.Log("==> Checking for new time");
     yield return StartCoroutine(
         TimeManager.sharedInstance.getTime()
     );
     updateTime();

     Debug.Log("==> Time check complete!");


 }


 //trggered on button click
 public void rewardClicked()
 {
     spinText.spinAmount += 30;
     Debug.Log("==> Claim Button Clicked");
     claimReward(RewardToEarn);
     PlayerPrefs.SetString("_timer", "Standby");
     StartCoroutine("CheckTime");
 }



 //update method to make the progress tick
 void Update()
 {
     if (_timerIsReady)
     {
         if (!_timerComplete && PlayerPrefs.GetString("_timer") != "")
         {
             _value -= Time.deltaTime * 1f / (float)_endTime.TotalSeconds;
             _progress.fillAmount = _value;

             //this is called once only
             if (_value <= 0 && !_timerComplete)
             {
                 //SendNotification1();
                 //CreateNotifChanel1()

                 //when the timer hits 0, let do a quick validation to make sure no speed hacks.
                 validateTime();
                 _timerComplete = true;

             }
         }
     }
 }



 //validator
 private void validateTime()
 {

     Debug.Log("==> Validating time to make sure no speed hack!");
     StartCoroutine("CheckTime");
     PlayerPrefs.SetInt("_date", TimeManager.sharedInstance.getCurrentDateNow());

 }




 private void claimReward(int x)
 {
     Debug.Log("YOU EARN " + x + " REWARDS");
 }
 void CreateNotifChanel1()
 {
     var b = new AndroidNotificationChannel()
     {
         Id = "spin",
         Name = "playreminder",
         Importance = Importance.High,
         Description = "Reminds the player to play the game",
     };
     AndroidNotificationCenter.RegisterNotificationChannel(b);
 }


 void SendNotification1()
 {
     var notification = new AndroidNotification();
     notification.Title = "Colect Reward Spin";
     notification.Text = "Come one and collect spin and win";
     notification.FireTime = System.DateTime.Now.AddSeconds(3);
     notification.SmallIcon = "icon_3";
     notification.LargeIcon = "icon_2";
     notification.ShouldAutoCancel = true;


     AndroidNotificationCenter.SendNotification(notification, "spin");
 }
 public void SaveData()
 {
     PlayerPrefs.SetString("_timer", TimeManager.sharedInstance.getCurrentTimeNow());
     PlayerPrefs.Save();
 }

 void OnApplicationPause(bool pauseStatus)
 {
     if (pauseStatus)
     {

         

     }


 }

}